A method for measuring the pitch angle of the core magnetic field of a magnetic confinement fusion device

Abstract

The application discloses a method for measuring a pitch angle of a magnetic field in a core of a magnetic confinement fusion device, which comprises the following steps: simultaneously emitting microwave signals of X-mode and O-mode polarization to plasma by a Doppler backscattering diagnostic system (DBS), and receiving scattered signals returned along a transmission light path; dividing the received scattered signals into two paths by a beam splitter, one of which enters the original DBS, and the other of which enters a rotatable antenna for selecting a vibration direction of an electric field component; adjusting an included angle between the vibration direction of the electric field component of the rotatable antenna and the vibration direction of the electric field component of the DBS transmission antenna according to the vibration direction of the electric field component of the DBS transmission antenna, obtaining the vibration direction of the electric field component of the backscattering signal through the ratio of the signal intensity received by the two antennas, and further obtaining the pitch angle of the magnetic field. The above method has the advantages of low cost, almost no interference to plasma, high time resolution, and can be used for real-time measurement of the pitch angle of the magnetic field in the core of the magnetic confinement fusion device without interference.

Description

Technical Field

[0001] This invention relates to the field of microwave diagnostic technology, and in particular to a method for measuring the pitch angle of the magnetic field in the core of a magnetic confinement fusion device. Background Technology

[0002] Driven by the need to address climate change and achieve sustainable energy development, controlled nuclear fusion is considered one of the most promising clean energy solutions for the future. Fusion energy boasts advantages such as abundant fuel, zero carbon dioxide emissions, and long-term stable operation. Currently, the most promising path to its realization is the magnetic confinement fusion device. Magnetic confinement fusion devices rely on strong magnetic fields to confine high-temperature plasma, and their confinement performance and stability directly determine the feasibility of fusion energy. In magnetic confinement fusion physics, EFIT (Equilibrium Fitting Code, a computer program for reconstructing the two-dimensional equilibrium configuration of plasma) equilibrium reconstruction is the foundation for many subsequent analyses. Turbulent transport simulations, magnetohydrodynamic (MHD) stability calculations, and studies of fast ion behavior all require accurate magnetic field structures. However, EFIT obtains the tokamak magnetic field distribution by solving the Grad–Shafranov equations, which require experimental measurements for confinement. The magnetic field pitch angle is a key physical quantity used for EFIT equilibrium reconstruction in magnetic confinement fusion devices.

[0003] Among existing methods for measuring the pitch angle of a magnetic field, Motional Stark Effect Spectroscopy (MSE) can directly measure the pitch angle of a magnetic field with high spatiotemporal resolution, but it requires the injection of a high-energy neutral beam (~50-10 keV) into a magnetic confinement fusion device, and the supporting equipment is complex. Diagnostic systems such as Faraday Rotation Polarimetry, Magnetic Probes (Mirnov Coils), and Electron Cyclopolar Interference Measurement (ECEI / POINT) have low spatiotemporal resolution and rely on other diagnostic methods to indirectly measure the pitch angle of a magnetic field. Summary of the Invention

[0004] The purpose of this invention is to provide a method for measuring the magnetic field pitch angle of the core of a magnetic confinement fusion device. This method is low-cost, causes almost no interference to the plasma, has high time resolution, and can measure the magnetic field pitch angle of a local location in the core of a magnetic confinement fusion device in real time without interference.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for measuring the pitch angle of the magnetic field in the core of a magnetic confinement fusion device, the method comprising:

[0007] Step 1: Simultaneously transmit X-mode and O-mode polarized microwave signals to the plasma through the Doppler backscattering meter diagnostic system (DBS), and receive the scattered signals returning along the transmitted optical path;

[0008] Step 2: The received scattered signal is split into two paths by a beam splitter. One path goes into the original DBS, and the other path goes into a rotatable antenna to adjust the vibration direction of the received electric field component.

[0009] Step 3: Based on the vibration direction of the electric field component of the DBS transmitting antenna, adjust the angle between the vibration direction of the electric field component of the rotatable antenna and the vibration direction of the electric field component of the DBS transmitting antenna. By comparing the signal strength received by the two antennas, the vibration direction of the electric field component of the backscattered signal can be obtained, and thus the pitch angle of the magnetic field in the core of the magnetic confinement fusion device can be obtained.

[0010] As can be seen from the technical solution provided by the present invention, the above method is low in cost, has almost no interference with plasma, has high time resolution, and can measure the magnetic field pitch angle of the local position of the core of the magnetic confinement fusion device in real time without interference. Attached Figure Description

[0011] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic flowchart of a method for measuring the pitch angle of the magnetic field in the core of a magnetic confinement fusion device, provided in an embodiment of the present invention.

[0013] Figure 2 This is a schematic diagram of the microwave circuit used in the example of this invention.

[0014] Figure 3 This is a schematic diagram illustrating the process of measuring the magnetic field pitch angle in an example of the present invention. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments, and do not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0016] like Figure 1The diagram shown is a flowchart illustrating a method for measuring the pitch angle of the magnetic field in the core of a magnetic confinement fusion device according to an embodiment of the present invention. The method includes:

[0017] Step 1: Simultaneously transmit X-mode and O-mode polarized microwave signals to the plasma through the Doppler backscattering meter diagnostic system (DBS), and receive the scattered signals returning along the transmitted optical path;

[0018] In this step, the Doppler Backscattering (DBS) diagnostic system controls the electric field component E of the emitted microwaves by setting the frequency of the microwaves emitted by the electronics system. i O-mode component E i sin(θ+β) penetrates the plasma, where θ represents the magnetic field pitch angle to be measured, and β represents the electric field component of the emitted microwave and the poloidal magnetic field B. P The included angle;

[0019] The electric field component E of the emitted microwave i X-mode component E i cos(θ+β) is scattered at the cutoff layer, and the scattered signal that returns to the transmitting antenna along the transmitted light path and is received is called the backscattered signal. Among them, considering the propagation of microwaves in plasma, when the refractive index of microwaves becomes 0 or the wavenumber k approaches 0, microwaves are cut off in plasma and reflected at the cutoff point. For a tokamak device, such a cutoff point is a density profile with the same density and magnetic field, and is therefore called the cutoff layer.

[0020] The scattered signal received by the DBS optical front end along the emitted optical path is the X-mode signal E relative to the background magnetic field at the cutoff layer. i cos(θ+β), since the vibration direction of the electric field component of the X-mode signal is perpendicular to the direction of the background magnetic field at the cutoff layer, the vibration direction of the electric field component of the backscattered signal carries the information of the magnetic field pitch angle θ.

[0021] The Doppler backscattering diagnostic system (DBS) used in the specific implementation can be used to measure parameters such as local density fluctuations and radial distribution of velocity fluctuations.

[0022] Step 2: The received scattered signal is split into two paths by a beam splitter. One path goes into the original DBS, and the other path goes into a rotatable antenna to adjust the vibration direction of the received electric field component.

[0023] In this step, when the angle between the vibration direction of the electric field component of the rotatable antenna and the vibration direction of the electric field component of the backscattered signal is... At that time, according to the orthogonal decomposition, the scattered signal received by the rotatable antenna is the electric field component of the returned backscattered signal. Components, and formulas for calculating electromagnetic wave intensity Here, I is the average intensity of the electromagnetic wave; n is the refractive index of the medium. is the dielectric constant in a vacuum; c is the speed of light in a vacuum. It is the peak value of the electric field intensity of electromagnetic waves, and it is a definite value when orthogonally decomposed;

[0024] Therefore, the electric field component intensity of the backscattered signal received by the rotatable antenna and Proportional, expressed as:

[0025] .

[0026] Step 3: Based on the vibration direction of the electric field component of the DBS transmitting antenna, adjust the angle between the vibration direction of the electric field component of the rotatable antenna and the vibration direction of the electric field component of the DBS transmitting antenna. By comparing the signal strength received by the two antennas, the vibration direction of the electric field component of the backscattered signal can be obtained, and thus the pitch angle of the magnetic field in the core of the magnetic confinement fusion device can be obtained.

[0027] In this step, specifically, the vibration direction of the electric field component of the rotatable antenna is rotated to an angle of (90-α-β)° with the vibration direction of the electric field component of the DBS transmitting antenna; under these conditions, the intensity of the electric field component of the backscattered signal received by the rotatable antenna is... The following relationship exists:

[0028] ;

[0029] Electric field component intensity of the backscattered signal received by the DBS transmitting antenna The following relationship exists:

[0030] ;

[0031] The ratio of the signal strength received by the two antennas is expressed as:

[0032] ;

[0033] Where α is the relative circumferential magnetic field B of the rotatable antenna set in the experiment. T The angle; β represents the electric field component of the emitted microwave and the poloidal magnetic field B. P The angle between the magnetic field lines is used to calculate the pitch angle θ of the magnetic field in the core of the magnetic confinement fusion device. The specific process is as follows:

[0034] First, set the rotatable antenna relative to the circumferential magnetic field B. T Angle Determine the ratio coefficient of the received signal strength between the two antennas. Specifically:

[0035] ;

[0036] Relationship obtained:

[0037] ;

[0038] Then set another rotatable antenna relative to the circumferential magnetic field B. T Angle ,calculate

[0039] ;

[0040] The final calculation yielded the screw angle θ of the magnetic field in the core of the magnetic confinement fusion device.

[0041] In practice, considering that the signal strength of the DBS transmitting antenna and the rotatable antenna is also related to factors such as the beam splitter ratio, amplifier gain, and data acquisition card, the angle between the vibration direction of the electric field component of the rotatable antenna and the vibration direction of the electric field component of the DBS transmitting antenna is adjusted to 0° before measurement. This is used to calibrate the differences in signal strength between the DBS transmitting antenna and the rotatable antenna caused by the beam splitter ratio, amplifier gain, and data acquisition card.

[0042] In addition, the rotatable antenna employs a scattering signal receiving system that can quickly select the polarization direction. The polarization direction can be adjusted by rotating the platform, thereby adjusting the vibration direction of the electric field component of the backscattered signal.

[0043] It is worth noting that the contents not described in detail in the embodiments of the present invention belong to the prior art known to those skilled in the art.

[0044] This invention also provides an electronic device, including a memory and a processor, wherein the memory stores a computer program and the processor is configured to run the computer program to perform the method.

[0045] This invention also provides a computer storage medium storing a plurality of instructions adapted for loading and executing the method by a processor.

[0046] The measurement method described in this embodiment of the invention will be illustrated below with specific examples. This example uses an integrated microwave system that receives backscattered signals via E-band backscattering and selectable electric field component vibration direction. Figure 2 The figure shows a schematic diagram of the microwave circuit of the example of the present invention. The part in rectangle (1) is the multi-channel microwave generation and transmission system; the parts in rectangle (2) and rectangle (3) are the DBS and the receiving system (rotatable antenna) with selectable backscattered electric field component vibration direction, respectively. The specific reference numerals are shown in Table 1 below:

[0047] Table 1 Names of each component

[0048]

[0049] A signal generator (No. 10) is used as a reference microwave signal, i.e., a backscattering reference source, due to its low cost, portability, and good stability. The LMS-183DX model is an adjustable microwave source with a frequency range of 6-18 GHz as the reference microwave signal. A hollow rotating platform (No. 21) has a maximum rotation speed of 78° / s, a repeatability of 0.005°, can rotate 360°, and has a hollow diameter of 90 mm. Therefore, the hollow rotating platform is used as a fast rotating carrier to carry the receiving antenna to select the vibration direction of the electric field component of the backscattered signal. This is one of the keys to the measurement of the magnetic field pitch angle in this application.

[0050] The signal output is divided into three parts: the reference signal (LO) is mixed with the backscattered received signals in signal mixers (numbered 13 and 22) to obtain an intermediate frequency (IF) signal (which serves as the RF input of the I / Q mixer (numbered 15)); the reference signal is mixed with the transmitted signal in the reference mixer (numbered 12) to obtain an IF signal (which serves as the LO input of the I / Q mixer). In the microwave system's generation and transmission system, the microwave source (numbered 1) outputs a frequency range of 1-2 GHz, with a minimum adjustable frequency step of 1 MHz. In the experiment, the signal source output was set to 2.0 GHz. Using a bandpass filter (number 3) with a frequency range of 15-23 GHz, four specific frequencies of 16, 18, 20, and 22 GHz were selected from the output of the comb spectrum generator (number 2). These four fixed frequencies (16, 18, 20, and 22 GHz) were then further frequency-multiplied and optimized by a frequency multiplier (number 5) and an EH tuner (number 6) to achieve a frequency range of 60-90 GHz (E-band, frequency interval Δf = 2.0 GHz). Therefore, 16 fixed-frequency microwaves were emitted into the plasma, all of which can be considered as probe microwave beams.

[0051] In the receiving section (part 2) of the DBS, the transmitting antenna (number 9) also serves as the receiving antenna for the DBS. The received signal is then mixed with the reference signal in a backscattered signal mixer (number 13) to obtain the intermediate frequency (IF) signal. The down-converted IF signals from the reference mixer (number 12) and the signal mixer are both passed through a low-pass filter (0-2 GHz).

[0052] In the receiving section (3 parts) of the receiving system with selectable vibration direction of the backscattered electric field component, a separate antenna (number 20) is used to receive the backscattered signal. Its polarization direction can rotate with the rotating platform, thereby selecting the vibration direction of the electric field component of the backscattered signal. The received signal is then mixed with a reference signal in a scattered signal mixer (number 22) to obtain an intermediate frequency signal. In the specific implementation, Figure 2 The detection frequencies of the DBS and the receiver system with selectable backscattered electric field component vibration direction are respectively and By changing To change the detection frequency.

[0053] The intermediate frequency signals from the reference path and the receiving path are demodulated into Acosφ and Asinφ (IQ signals, where A is the amplitude of the received backscattered signal and Φ is the phase of the backscattered signal) in the I / Q mixer (No. 15). The IQ signals are acquired by the high-speed data stream system (No. 17).

[0054] like Figure 3 The diagram shown is a schematic diagram of the process of measuring the magnetic field pitch angle in an example of the present invention. In the diagram, B... P This represents the poloidal magnetic field at the location of the microwave cutoff layer in a magnetic confinement fusion device; the arrow indicates its direction. T This represents the circumferential magnetic field at the location of the microwave cutoff layer in a magnetic confinement fusion device; the arrow indicates its direction. P and B T These are the components in two directions obtained by orthogonal decomposition of the magnetic field B0 at the cutoff layer; E i The arrow represents the electric field component of the emitted microwave, indicating the direction, and β represents the electric field component E of the emitted microwave. i With the polar magnetic field B P The angle between them. Figure 3 In (1), the dashed line indicates the direction of the polar magnetic field. DBS controls the transmitted microwave E by setting the frequency of the microwave emitted by the electronic system. i O-mode component E i sin(θ+β) breaks through the plasma, X-mode component E i cos(θ+β) is scattered at the cutoff layer; therefore, the scattered signal received by the optical front end of the DBS system is the X-mode signal E relative to the background magnetic field at the cutoff layer. i cos(θ+β).

[0055] Based on the DBS, the scattered signal is split into two paths by a beam splitter. One path enters the original DBS, and the other path enters a rotatable antenna to select the vibration direction of the received electric field component. When the vibration direction of the electric field component of the rotatable antenna is at an angle α with the vibration direction of the electric field component of the backscattered signal, according to the orthogonal decomposition and electromagnetic wave intensity calculation formula, the intensity of the scattered signal received by the rotatable antenna is related to (cos(α)). 2 Proportional, α is the relative circumferential magnetic field B of the rotatable antenna set in the experiment. T The angle.

[0056] exist Figure 3 In (2), the two dashed lines represent the vibration directions of the electric field components of the DBS transmitting antenna and the rotatable antenna, respectively. Given the vibration direction of the DBS transmitting antenna's electric field component, rotate the rotatable antenna's electric field component vibration direction until the angle between it and the DBS transmitting antenna's electric field component vibration direction is (90-α-β)°. The ratio of the received signal strengths of the two antennas is... Thus, the pitch angle θ of the magnetic field in the core of the magnetic confinement fusion device can be calculated.

[0057] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims. The information disclosed in the background section is intended only to enhance the understanding of the overall background technology of the present invention and should not be construed as an admission or implication in any way that such information constitutes prior art known to those skilled in the art.

Claims

1. A method of measuring the pitch angle of the core magnetic field of a magnetic confinement fusion device, characterized in that, The method includes: Step 1: Simultaneously transmit X-mode and O-mode polarized microwave signals to the plasma through the Doppler backscattering meter diagnostic system (DBS), and receive the scattered signals returning along the transmitted optical path; Step 2: The received scattered signal is split into two paths by a beam splitter. One path goes into the original DBS, and the other path goes into a rotatable antenna to adjust the vibration direction of the received electric field component. Step 3: Based on the vibration direction of the electric field component of the DBS transmitting antenna, adjust the angle between the vibration direction of the electric field component of the rotatable antenna and the vibration direction of the electric field component of the DBS transmitting antenna. By comparing the signal strength received by the two antennas, the vibration direction of the electric field component of the backscattered signal can be obtained, and thus the pitch angle of the magnetic field in the core of the magnetic confinement fusion device can be obtained. In step 3, specifically, the vibration direction of the electric field component of the rotatable antenna is rotated to an angle of (90-α-β)° with the vibration direction of the electric field component of the DBS transmitting antenna; under these conditions, the intensity of the backscattered signal electric field component received by the rotatable antenna is... The following relationship exists: ； The intensity of the backscattered signal electric field component received by the DBS transmit antenna There is a relationship: ； The ratio of the signal strength received by the two antennas is: ； Where α is the relative circumferential magnetic field B of the rotatable antenna set in the experiment. T The angle; β represents the electric field component of the emitted microwave and the poloidal magnetic field B. P The angle between the magnetic field lines is used to calculate the pitch angle θ of the magnetic field in the core of the magnetic confinement fusion device. The specific process is as follows: First, set the rotatable antenna relative to the circumferential magnetic field B. T Angle Determine the ratio coefficient of the received signal strength between the two antennas. Specifically: ； Relationship obtained: ； Then set the angle of another rotatable antenna relative to the ring magnetic field B T , calculate​ ； The final calculation yielded the screw angle θ of the magnetic field in the core of the magnetic confinement fusion device.

2. The method of measuring the pitch angle of the core magnetic field of a magnetic confinement fusion device according to claim 1, wherein, In step 1, the Doppler backscattering diagnostic system (DBS) controls the electric field component E of the emitted microwaves by setting the frequency of the microwaves emitted by the electronic system. i O-mode component E i sin(θ+β) penetrates the plasma; θ represents the magnetic field pitch angle to be measured, and β represents the electric field component of the emitted microwave and the poloidal magnetic field B. P The included angle; The electric field component E of the emitted microwave i The X-mode component E of the electric field of the emitted microwave i cos(θ+β) is scattered at the cut-off layer and returns along the emission path to the emission antenna, the scattered signal received by the emission antenna being called backscattered signal; The scattered signal received by the DBS optical front end along the emitted optical path is the X-mode signal E relative to the background magnetic field at the cutoff layer. i cos(θ+β), since the vibration direction of the electric field component of the X-mode signal is perpendicular to the direction of the background magnetic field at the cutoff layer, the vibration direction of the electric field component of the backscattered signal carries the information of the magnetic field pitch angle θ.

3. The method of measuring the pitch angle of the core magnetic field of a magnetic confinement fusion device according to claim 2, wherein, In step 2, When the angle between the vibration direction of the electric field component of the rotatable antenna and the vibration direction of the electric field component of the backscattered signal is... At that time, according to the orthogonal decomposition, the scattered signal received by the rotatable antenna is the electric field component of the returned backscattered signal. Components, and formulas for calculating electromagnetic wave intensity Here, I is the average intensity of the electromagnetic wave; n is the refractive index of the medium. is the dielectric constant in a vacuum; c is the speed of light in a vacuum. It is the peak value of the electric field intensity of electromagnetic waves, and it is a definite value when orthogonally decomposed; The intensity of the backscattered signal electric field component received by the rotatable antenna is therefore proportional to is proportional to is proportional to 。 4. The method of measuring the pitch angle of the core magnetic field of a magnetic confinement fusion device according to claim 1, wherein, In step 3, before the measurement is performed, the angle between the vibration direction of the electric field component of the rotatable antenna and the vibration direction of the electric field component of the DBS transmitting antenna is adjusted to 0°, thereby calibrating the difference in signal strength between the DBS transmitting antenna and the rotatable antenna caused by the beam splitter ratio, amplifier gain, and acquisition card.

5. The method of measuring the pitch angle of the core magnetic field of a magnetic confinement fusion device according to claim 1, wherein, The rotatable antenna employs a scattered signal receiving system that can quickly select the polarization direction. The polarization direction can be adjusted by rotating the platform, thereby adjusting the vibration direction of the electric field component of the backscattered signal.

6. An electronic device comprising a memory and a processor, characterized in that The memory stores a computer program, and the processor is configured to run the computer program to perform the method according to any one of claims 1 to 5.

7. A computer storage medium, characterized in that The computer storage medium stores a plurality of instructions adapted for loading by a processor and executing the method of any one of claims 1 to 5.

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